Male primates may have become monogamous to protect their offspring from being killed by rival males, a new study finds. However, others disagree, saying monogamy evolved in mammals so that males could guard their mates.

A team of British and Australian researchers compared data across 230 primate species over 75 million years, and found that the threat of infanticide -- specifically, the threat of baby primates being killed by unrelated males -- likely triggered monogamy.